Moony, Wormtail, Padfoot and Prongs, four wizards who went to Hogwarts. Prongs, (James Potter), Padfoot (Sirius Black), Wormtail (Peeter Petigrew) were all animagus, unregistered, of course. Moony (Professor Romulus Lupin), was a werewolf, and they created this map so they could sneak out and not be caught.

Alastor Moody, (aka Mad Eye Moody) the defense against the dark arts teacher in Harry's fourth year has a magical eye instead of a real one, which zooms around, can see through invisibility cloaks, and through solid walls.

The 3 hallows from the tale of the 3 brothers, the elder wand, the resurrection stone, and the invisibility cloak, the three hallows that if one person is in possession of them all, they are the master of death. Harry Potter's invisibility cloak is the 3rd hallow.

This hat sorts the new students at Hogwarts into their houses, Gryffindor, Ravenclaw, Slytherin, and Hufflepuf. When harry arrives at Hogwarts, the hat says that he will do good in Slytherin. Harry asks to not be in Slytherin, and the hat obliges, sorting him into Gryffindor.

In the second book, Lucius malfoy drops a small diary into Ginny's cauldron. The diary is actually a horcrux, and the bit of Tom Riddle's soul in it flits in and out of the case, occasionally possessing Ginny and making her open the chamber of secrets. It is destroyed by Harry Potter with a basilisk fang.